Old fashioned hoist.......advice reqd!!

[weston29]

Hi All new to the site, so be gentle!!!

Work as an industrial electrician, just started for myself. Been in the game 10 years now, and counting!

Came across a job last week on a workshop hoist (three phase). The owner said it had broken down and was travelling left and right, lifting up but not coming down. I have worked on a few of these things in the past but this thing is as old as the hills. Checked it out and there was no evidence of anything untoward. Motor meggered out ok, connections all good and tight. The switch gear ive never seen before. Like a really old fashioned contactor ( i think?) and no evidence of an overload. All three phases present after checking. I think it may have a clutch on it. Its making a humming noise when the down button is pressed on the pendant, but hoist not coming down?!

Sounds like the rotor is stalled, think it may be a mechanical seizure of some description. Any ideas would be most apreciated!!!!

 

[mrloy99]

Hi All new to the site, so be gentle!!!

Work as an industrial electrician, just started for myself. Been in the game 10 years now, and counting!

Came across a job last week on a workshop hoist (three phase). The owner said it had broken down and was travelling left and right, lifting up but not coming down. I have worked on a few of these things in the past but this thing is as old as the hills. Checked it out and there was no evidence of anything untoward. Motor meggered out ok, connections all good and tight. The switch gear ive never seen before. Like a really old fashioned contactor ( i think?) and no evidence of an overload. All three phases present after checking. I think it may have a clutch on it. Its making a humming noise when the down button is pressed on the pendant, but hoist not coming down?! (quote)
would it perhaps be a faulty contactor? Should be able to manually push in,and it should go.I would imagine you would have 2 contactors with the second one having a different sequance of phases in order to reverse direction,same sort of set up as a rollerdoor.You would also have limit switches and maybe a door contact in series with the control circuit,You might also have a brake circuit.I don't know what you mean by travelling left and right?

 

[weston29]

Hi All new to the site, so be gentle!!!

Work as an industrial electrician, just started for myself. Been in the game 10 years now, and counting!

Came across a job last week on a workshop hoist (three phase). The owner said it had broken down and was travelling left and right, lifting up but not coming down. I have worked on a few of these things in the past but this thing is as old as the hills. Checked it out and there was no evidence of anything untoward. Motor meggered out ok, connections all good and tight. The switch gear ive never seen before. Like a really old fashioned contactor ( i think?) and no evidence of an overload. All three phases present after checking. I think it may have a clutch on it. Its making a humming noise when the down button is pressed on the pendant, but hoist not coming down?! (quote)
would it perhaps be a faulty contactor? Should be able to manually push in,and it should go.I would imagine you would have 2 contactors with the second one having a different sequance of phases in order to reverse direction,same sort of set up as a rollerdoor.You would also have limit switches and maybe a door contact in series with the control circuit,You might also have a brake circuit.I don't know what you mean by travelling left and right?

Left & right, I mean in and out on the travel, its got two motors, one to drive the beam trolley with the other for lifting the hook. Couldnt see no evidence of limit switches or door switches, it is literally the oldest one ive ever seen , but will have a proper look tommorow, im back down on the same job so will have a good go at tryin to get it away. The motor sounds like its trying to go which would surely rule out an open switch in the control circuit though would it not? Its making a humming sound, but no action from the hook when you press down on the pendant? Something youve come across before?

 

[mrloy99]

Left & right, I mean in and out on the travel, its got two motors, one to drive the beam trolley with the other for lifting the hook. Couldnt see no evidence of limit switches or door switches, it is literally the oldest one ive ever seen , but will have a proper look tommorow, im back down on the same job so will have a good go at tryin to get it away. The motor sounds like its trying to go which would surely rule out an open switch in the control circuit though would it not? Its making a humming sound, but no action from the hook when you press down on the pendant? Something youve come across before?

sounds like a gantry crane you have there rather than a goods hoist!lol.
I have done a bit on these a few years ago.5o% of faults were down to the wires breaking inside the "pendant control".Do you know if the hum is from the contactors or the motor?
You would need to check at the terminals going to the motor that you are getting full voltage on all phases,going both directions.If you are then that should illiminate any controls and would suggest faulty motor.(if i remember right there might be a manual release for to let out some cable,and a limit switch)If the motor needs work done,rewind,bushes etc you will have fun trying to get it down!! Your clutch or brake could also be the culprit,often work at 2 phase 400volt coil

 

[wattsup]

Mains reversing contactor is not working correctly, most likely a burn-out on one of the connections. It could be a faulty motor winding but I have never seen. Its easy to check, on hoist and lower. Check 415v at motor between all phases, hoist or low, I bet on lower you aint got 415 v, hence the reversing contactor is not providing the feed. It is a common fault. Do it manually, reverse 2-phases and see if the motor runs in opposite directions

Also a limit switch could be the problem...(forgot to mention)

Humming on down suggests a phase down

 

[weston29]

Had a look today, didnt have any contactors, the phase reversing for the motor up and down was done in the pendant. The fault was that there was a loose connection (or two!), at the motor terminal, which had in turn generated heat at the N/O push button and welded the contacts internally. When the button for the down was being pressed there was a phase down at the motor and so thats how i found it. Took a while though!

Changed the contact blocks and made all connections good at the motor end. Gave a load check with a weght on the hoist and gave good balanced load across three phases, within the rating. Have advised the owner to get updated newer hoists or rewire utilising contactors and an overload, but cant see him going for it. Thanks for the help guys.

 

[Guest123]

That hoist on loan from Noah was it???

 

[weston29]

well older mate! Noahs grandad!

 

[Guest123]

I knew him, used to work the checkout in morrissons, birkenhead

 

[stretchyboy]

Dont you just love the opportunistic salesmen .........

I'm resisting the urge to post a joke about the salesmen's name and those websites that you put your name in and it gives you your '---- star' alternative identity

Sorry Jimmy... no offence!

 

[boatnik1]

Just to get back to the OP, I vaguely remember an old morris hoist with the contactors in the pendant which was a steel box suspended by a chain from the gantry. The system had to be changed because of H&S as the idea of a bunch of 440 wires in a steel box hanging down for operators to use and swing on, amounted to a potential hair straightener with a vengence. Changed the system by changeing the contactor coils for LV and fitting a LV transformer then raising the pendant box up to the crane and dropped a new LV pendant from the gantry.

 

[stretchyboy]

"Learn from the mistakes of others, You might not live long enough to make them all yourself.".

Ha Ha, very true.




That sounds like the ideal answer, and shouldn't be too costly either. Sometimes have to twist there arm to spend money but keep stressing the safety element and you should win the job